The influence of different compositional modifications on the magnetic entropy change and refrigerant capacity of Finemet, Nanoperm, HiTperm, and bulk amorphous alloys is presented. For all the studied alloys, the field dependence of the magnetic entropy change exhibits a quadratic dependence in the paramagnetic regime, a linear dependence in the ferromagnetic temperature range, and a potential law with a field exponent ϳ0.75 at the Curie temperature. This exponent can be explained using the critical exponents of the Curie transition. It is shown that for alloys of similar compositional series, the magnetic entropy change follows a master curve behavior. © 2007 American Institute of Physics. ͓DOI: 10.1063/1.2709409͔Magnetic refrigeration is a field of current interest due to the enhanced performance and reduced environmental impact of these systems when compared with those based on the gas compression-expansion cycle. 1-3 Although current prototypes are based on rare-earth-based materials, 4 soft magnetic amorphous alloys have been recently proposed as low cost candidates for high temperature magnetic refrigeration. [5][6][7][8][9][10][11][12][13] Albeit the maximum magnetic entropy change, ͉⌬S M pk ͉, for these alloys is modest when compared to that of rareearth-based materials, 14,15 the remarkable difference in material costs is an incentive for studying their suitability as magnetic refrigerants. Besides their reduced magnetic hysteresis ͑virtually negligible͒, higher electrical resistivity ͑which would decrease eddy current losses͒, tunable Curie temperature and, in the case of bulk amorphous alloys, outstanding mechanical properties are beneficial characteristics for a successful application of the material. The field dependence of the magnetic entropy change ⌬S M in materials with a second order phase transition has also been recently studied, demonstrating that a master curve behavior is fulfilled for ⌬S M curves measured up to different maximum fields. 16 The aim of this work is twofold: to present a comparison of the relevant characteristics of the magnetocaloric response of selected Finemet, Nanoperm, HiTperm, and bulk amorphous alloys ͑BAAs͒ prepared in ribbon shape and to demonstrate that ⌬S M ͑T͒ curves of different alloys from the same compositional series can also collapse in a master curve.Amorphous alloys from different compositional series have been prepared in ribbon shape ͑ϳ25 m thick͒ by melt spinning: Fe x Co

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This work aims at studying of electrochemical oxidation of porous silicon (PSi) and its behaviour in simulated body fluid (SBF). Continuing electrochemical oxidation of PSi introduces gradual changes in morphology of the porous structure and composition of PSi. As a result, interaction between this material and SBF is changed. As more oxidized is the PSi sample, slower is the dissolution process (biodegradability) and more easily it becomes covered by the calcium-phosphorous deposits from SBF (bioactivity). We observed that crystalline hydroxyapatite HA phase could be deposited in a very homogeneous manner onto OxPSi layers immersed in SBF at 36.5 o C during 30 days.

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